1. Field of the Invention
The present invention relates generally to a destructive method of disposing of unwanted legacy nuclear materials: surplus weapons grade plutonium and reactor grade plutonium, specifically. More particularly, the invention involves a thorium-plutonium-hydride fuel used with lead or lead alloy coolants in a fast spectrum reactor. Still more particularly, the invention relates to a lightly hydrided/deuterated metallic plutonium-thorium fuel for use in a fast fission pool-type nuclear reactor cooled with liquid metal coolants, preferably including lithium-7 lead eutectic, lead bismuth eutectic or lead. Plutonium-239 is consumed, and merchantable heat is produced along with fissile uranium-233, which can be denatured with uranium-238 and used in light water reactors as fuel.
2. Discussion of Related Art Including Information Disclosed Under 37 CFR §§1.97, 1.98
The general principles governing epi-thermal and fast spectrum nuclear reactors are well known in the art. In the earliest years of the nuclear era, nuclear physicists, chemists, and engineers noted that fast spectrum reactors have advantages over thermal-spectrum nuclear reactors. The neutron capture cross sections of elements used as structural, coolant and cladding materials for the reactors (generally elements bearing atomic numbers 11 to 83) are significantly smaller in the harder energy spectra than in the thermal spectrum. Further, no neutrons are lost by hydrogen capture to light water. U.S. Pat. No. 2,993,850, to Soodak, et al (issued Jul. 25, 1961) teaches that parasitic neutron capture is significantly reduced in fast reactors, and therefore a much greater neutron economy is achievable when the reactor is designed for the fast neutron spectrum.
Linton Lang conceived of a fast breeder reactor intended to produce “clean” uranium-233 (uranium-233 without co-produced uranium-232). U.S. Pat. No. 3,658,644, to Lang, discloses a fast breeder reactor designed to produce clean uranium-233, wherein the fuel production and power functions are separated in the reactor design. The fast reactor shown obtains its power mostly from fast fission of the fissile material in the fuel. The '644 patent teaches a moderator partition demising the power production region of the central core of the reactor from a thorium-containing blanket on the other side of the partition. The purpose was to eliminate most of the energetic fission neutrons and those neutrons having sufficient energy to produce n, 2n reactions with the thorium blanket. The moderators suggested for the inventive partition included zirconium hydride and lithium-7.
U.S. Pat. No. 4,393,510, to Lang, et al, discloses a light water reactor and a process to produce uranium-233 with less than 10 parts per million of uranium-232. The patent teaches that the production of uranium-232 in uranium-233 can be suppressed by separating a thorium-232 reactor blanket from the nuclear fuel using a moderator partition that reduces the energy of the incident neutrons below an energy threshold of 6 million electron volts (6 MeV). The importance of the teachings in the '510 patent resides in the fact that uranium-232, when present in concentrations over 10 parts per million, makes fuel unfit for glove-box handling as the gamma radiation from thallium-208 is too high for worker safety. Of equal importance in the teaching is the fact that the amount of co-produced uranium-232 is a function of the number interactions between thorium-232 atoms and neutrons that have energy exceeding 6 MeV. Significantly, however, the '510 patent deals with the use of a water cooled reactor, a thermal spectrum reactor, and not a liquid metal cooled reactor, as employed in the present application.
Another early patent, U.S. Pat. No. 2,904,429, to Schonfeld, discusses means and methods to fabricate binary alloys of thorium and plutonium and shows that when thorium atoms constitute 85% or more of the binary thorium-plutonium alloy, the compound possesses a face-centered cubic crystalline structure that is stable at elevated temperature. When the percentage of thorium exceeds 85%, the binary alloy is stable at temperatures exceeding 900 degrees C. The '429 patent shows that a plutonium-thorium compound is an excellent metallic nuclear fuel.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.